Nektar Announces Positive Prelim. Data for NKTR-102 in Ovarian Cancer

SAN CARLOS, Calif., March 8, 2010 -- Nektar Therapeutics
(Nasdaq: NKTR) today announced preliminary progression-free
survival data from the first stage of a two-stage Phase 2 clinical
study evaluating single-agent treatment with NKTR-102 in women with
platinum-resistant ovarian cancer. In the first stage of the study,
39 patients were enrolled with platinum-resistant disease and were
evaluable for the secondary endpoint of progression-free survival
(PFS).

The study showed that women who received NKTR-102 once every 21
days (q21 day) had a median PFS of 21.0 weeks. In the second arm of
the study, women who received NKTR-102 once every 14 days (q14 day)
had a median PFS of 12.2 weeks. Progression-free survival is a
measure of how long patients live without their disease advancing.
Current agents approved by the U.S. Food & Drug Administration
to treat women with platinum-resistant ovarian cancer have median
PFS of between 9.1 and 13.6 weeks.(1)

"NKTR-102 has demonstrated a progression-free survival time of
nearly five months, which is remarkable for a largely refractory
population that is expected to have a PFS of less than three
months," said Lorianne Masuoka, M.D., Senior Vice President and
Chief Medical Officer. "With a confirmed objective GCIG response
rate of 35 percent also in the every three week dose schedule and a
favorable toxicity profile, NKTR-102 appears to offer great promise
to women with chemo-resistant ovarian cancer. We look forward to
sharing additional data when all patients have concluded both
stages of the study."

77% of the 39 women in the first stage of the NKTR-102 Phase 2
study had progressed within three months of their last platinum
dose and half of these patients had actually progressed within
three weeks of their last platinum regimen. There are patients in
the first stage of the study still receiving treatment with
NKTR-102.

In January, Nektar reported initial data from the first stage of
the Phase 2 study for the primary endpoint of overall response rate
using Gynecologic Cancer InterGroup (GCIG) criteria, i.e., a
combination of response by tumor imaging (RECIST) and/or ovarian
cancer biomarker (CA-125) criteria.(2) Women in the first stage of
the study showed an overall GCIG response rate of 32% (6/19) in the
once every 14 days (q14 day) dose schedule and 35% (7/20) for the
once every 21 days (q21 day) dose schedule. Confirmed objective
response rates using RECIST were 21% (4/19) and 22% (4/18) for the
q14 day and q21 day dose schedules, respectively. CA-125 response
rates were 31% (5/16) and 38% (6/16), for the q14 day and q21 day
dose schedules, respectively.

The most commonly observed grade 3 or grade 4 side effects in
the study to date (every 14 day/every 21 day dose schedule) were
diarrhea (29%/10%) and neutropenia (14%/10%).

The Phase 2 study has now completed enrollment with a total of
71 patients treated. The study is ongoing. Full data are expected
to be presented at a major scientific conference in 2010.

About the Study

The Phase 2 study is evaluating two dose regimens (q14 day and
q21 day) of single-agent NKTR-102 in women with platinum-resistant
ovarian cancer. The study employs a two-stage design, with 41
patients in the first stage and 30 patients in the second stage.
Two patients in the q14 day dose regimen in the first stage had
platinum-sensitive disease and were not evaluable for the primary
outcome measure. The primary endpoint for the study is overall
response rate using Gynecologic Cancer InterGroup (GCIG) criteria,
a combination of response by tumor imaging (RECIST) and/or ovarian
cancer biomarker (CA-125) criteria. Secondary endpoints of the
Phase 2 study include progression-free survival and safety.

CA-125 is a biochemical marker that is found in the blood of
ovarian cancer patients and is measured to assess disease
progression and recurrence. RECIST classifies response based upon
tumor reduction measured by imaging methods.

Ovarian cancer is the fifth leading cause of cancer deaths among
women, accounting for more deaths than any other cancer of the
female reproductive system.(3) Agents currently approved by the
U.S. Food & Drug Administration to treat women with
platinum-resistant ovarian cancer also have modest overall response
rates of between 6.5 to 13.8%.(1), (4)

About NKTR-102

Nektar is developing NKTR-102, a topoisomerase I
inhibitor-polymer conjugate with reduced peak concentrations and a
continuous concentration profile. NKTR-102 was invented by Nektar
using its advanced polymer conjugate technology platform, and is
the first oncology product candidate to leverage Nektar's
releasable polymer technology platform.

In addition to the fully-enrolled Phase 2 study currently
ongoing in platinum-resistant ovarian cancer, NKTR-102 is also
being tested in two separate Phase 2 clinical trials in patients
with metastatic breast cancer and second-line colorectal
cancer.

About Nektar

Nektar Therapeutics is a biopharmaceutical company developing
novel therapeutics based on its PEGylation and advanced polymer
conjugation technology platforms. Nektar's technology and drug
development expertise have enabled nine approved products in the
U.S. or Europe for leading biopharmaceutical company partners,
including UCB's Cimzia(R) for Crohn's disease and rheumatoid
arthritis, Roche's PEGASYS(R) for hepatitis C and Amgen's
Neulasta(R) for neutropenia.

Nektar has created a robust pipeline of potentially high-value
therapeutics to address unmet medical needs by leveraging and
expanding its technology platforms to improve and enable molecules.
Nektar is currently conducting clinical and preclinical programs in
oncology, pain and other therapeutic areas. In addition to the
releasable polymer technology used in NKTR-102, Nektar is the first
company to create a permanent small molecule-polymer conjugate with
enhanced oral bioavailability and restricted entry into the CNS.
Nektar recently entered into an exclusive worldwide license
agreement with AstraZeneca for its oral NKTR-118 program to treat
opioid-induced constipation and its NKTR-119 program for the
treatment of pain without constipation side effects. NKTR-105,
Nektar's second oncology program developed using its proprietary
small molecule advanced polymer conjugate technology, is in a Phase
1 clinical study in cancer patients with refractory solid
tumors.

Nektar is headquartered in San Carlos, California, with
additional R&D operations in Huntsville, Alabama and Hyderabad,
India. Further information about the company and its drug
development programs and capabilities may be found online at
http://www.nektar.com<http://www.nektar.com/>.

This press release contains forward-looking statements that
reflect the company's current views regarding the potential of the
company's technology platforms, the potential of NKTR-102 as a drug
candidate, preliminary results from stage 1 of a Phase 2 clinical
study for NKTR-102 in ovarian cancer.. These forward-looking
statements involve substantial risks and uncertainties, including
but not limited to one or more of the following: (i) NKTR-102 is in
early stage clinical development and the risk of failure remains
high and failure can unexpectedly occur at any stage for one or
more of the cancer indications being studied (i.e. ovarian cancer,
breast cancer, and colorectal cancer) prior to regulatory approval
due to efficacy, safety or other factors; (ii) the timing or
success of the commencement or end of clinical trials and
commercial launch of new drugs may be delayed or unsuccessful due
to regulatory delays, clinical trial design, slower than
anticipated patient enrollment, drug manufacturing challenges,
changing standards of care, clinical outcomes, or delay or failure
in obtaining regulatory approval in one or more important markets;
(iii) the preliminary Phase 2 results for NKTR-102 in ovarian
cancer patients in stage 1 described in this press release is
preliminary data only and remains subject to final data gathering
and analysis review procedures; (iv) the preliminary results from
stage 1 of the NKTR-102 clinical study for ovarian cancer is not
necessarily indicative or predictive of the future results from
stage 2 of this clinical study and therefore the outcome of the
final clinical study results for NKTR-102 in ovarian cancer remains
uncertain; (v) the company's patent applications for its
proprietary or partner product candidates may not issue, patents
that have issued may not be enforceable, or intellectual property
licenses from third parties may be required in the future; (vi) the
data from clinical studies in Nektar-102 from any particular cancer
indication is not necessarily predictive of the outcomes for other
cancer indications for which NKTR-102 is being studied by the
company (i.e. breast and colorectal cancers); (vii) if Nektar is
unable to establish and maintain collaboration partnerships (such
as for NKTR-102) on attractive commercial terms or at all, the
company's business, results of operations and financial condition
could suffer; and (viii) the outcome of any existing or future
intellectual property or other litigation related to the company's
proprietary product candidates including without limitation
NKTR-102. Other important risks and uncertainties are detailed in
the company's reports and other filings with the Securities and
Exchange Commission, including its most recent Annual Report on
Form 10-K filed with the SEC on March 3, 2010. Nektar undertakes no
obligation to update forward-looking statements, whether as a
result of new information, future events or otherwise.